A1:The source and storage conditions of raw material is different ,so there may be a slight difference in color, which is a normal phenomenon. Products from our company have to undergo a rigorous inspection and sensory biology verification before sale, to ensure that all the indicators characteristics of the product is under enterprise standard to the extent permitted, not affect the test results.

Q2:

After pouring the liquid medium on the plate , medium seems hard to clot or coagulation time is longer, is it some problem with product quality?

A2: The reason may be:

The required hydration in the preparation process have not been done completely .That is to say distilled water is not boil sufficiently to dissolve agar. Because agar proportion, easily settle in the bottom of the bottle, if not fully shaken after high-temperature sterilization, it will lead to uneven upper agar culture gene content and difficult to set.

Q3:

Why some colonies of E. coli chromogenic medium color not shown above, but also confirmed through biochemical tests for E. coli (false negative)?

A3: E. CHROMOGENIC medium is based on the principle of specific enzyme of E. coli and design, 94% of E. coli have β- glucuronidase enzyme, with the chromogenic enzyme substrate medium role in the formation of blue-green colonies. And about 4% of the E. coli does not have β- glucuronidase enzymes, including concern O157: H7 Escherichia coli. Therefore, these E. coli can not be displayed on the color characteristic of E. coli chromogenic medium,it is possible of false-negative on the chromogenic medium. However, the traditional medium of the same can not avoid the problem of false negatives, such as: no gas or slow ferment lactose intolerance may also strain 44.5 ℃ false negatives in the conventional medium. For this small part of the E. coli can be detected using other methods.

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